Film forming apparatuses are used at liquid-phase film forming processes for manufacturing semiconductor devices, liquid crystal displays, and the like. In the liquid-phase film forming processes, the coating films formed on substrates such as wafers are required to have uniform film thicknesses of about 0.1 to 1.0 μm. The coating films are therefore usually formed by spin coating. The spin coating is a coating method of forming a coating film on a substrate by supplying a material to the center of the substrate and rotating the substrate at high speed to spread the material on the substrate surface.